CN115462037B

CN115462037B - Reducing EMI in PLCA-based networks by beacon time extension

Info

Publication number: CN115462037B
Application number: CN202180030194.8A
Authority: CN
Inventors: G·I·伊万诺夫
Original assignee: Microchip Technology Inc
Current assignee: Microchip Technology Inc
Priority date: 2020-08-26
Filing date: 2021-08-26
Publication date: 2024-04-30
Anticipated expiration: 2041-08-26
Also published as: US20230291606A1; WO2022046962A1; KR20230054792A; US20220070021A1; CN115462037A; US11700146B2; JP2023539042A; DE112021004490T5

Abstract

The present invention provides an apparatus that is communicatively coupled to other nodes in a network. The apparatus may include a control circuit configured to repeatedly issue a transmission cycle to the other node. A given transmission period may include at least one transmit time slot for each of the other nodes to transmit data. The control circuitry may be configured to initiate a transmission cycle by sending out a beacon signal to the other node. The control circuitry may be configured to determine when to transmit a beacon signal in a given transmission period by: determining that all of the other nodes have completed all associated transmit time slots in an immediately preceding transmission period, and delaying transmission of the beacon signal for the given transmission period based on the determination that the transmission of the other nodes is completed.

Description

Reducing EMI in PLCA-based networks by beacon time extension

Priority

The present application claims priority from U.S. provisional patent application No. 63/070,643, filed 8/26 in 2020, the contents of which are hereby incorporated by reference in their entirety.

Technical Field

The present disclosure relates to ethernet communications, and more particularly to reducing electromagnetic interference (EMI) in a PHY Layer Collision Avoidance (PLCA) supported network (compliant with the IEEE 802.3cg standard, also known as single twisted pair ethernet, 10SPE, or 10 BASE-T1S) using time expansion of beacons in the network.

Background

The 10SPE is a proposed standard currently being revised and developed. The 10SPE defines ethernet local area network, access local area network and metropolitan area network. The ethernet network is run at a selected operating speed; and uses a common Medium Access Control (MAC) specification and Management Information Base (MIB). Carrier sense multiple access with collision detection (CSMA/CD) MAC protocols specify shared medium (half duplex) operation as well as full duplex operation. A Media Independent Interface (MII) of a particular speed provides an architecture and optionally an implementation specific interface to a selected physical layer entity (PHY). The physical layer encodes frames for transmission and decodes received frames with a modulation specified for operating speed, transmission medium, and supporting link length. Other specified capabilities include: control and management protocols, and power over the selected twisted pair PHY type.

Disclosure of Invention

Examples of the present disclosure may include an apparatus. The apparatus may include a network interface. The network interface may be configured to communicatively couple the device to one or more other nodes in the network. The apparatus may include a control circuit configured to repeatedly issue a transmission cycle to other nodes over a network interface. A given transmission period may include at least one transmit time slot for each of the other nodes to transmit data. The control circuitry may be configured to initiate a transmission cycle by sending out a beacon signal to the other node. The control circuitry may be configured to complete transmissions by all other nodes by determining that all associated transmit slots have been completed in an immediately preceding transmission period, thereby determining when to transmit a beacon signal in a given transmission period. The control circuitry may be configured to delay transmission of the beacon signal for a given transmission period based on a determination that transmission of the other nodes is complete, thereby further determining when to transmit the beacon signal in the given transmission period.

Examples of the present disclosure may include repeatedly issuing, at a node in a network, a transmission cycle to other nodes in a network interface. A given transmission period may include at least one transmit time slot for each of the other nodes to transmit data. The method may include initiating a transmission cycle by sending out a beacon signal to other nodes. The method may include completing transmission of other nodes by determining that all other nodes have completed all associated transmit slots in an immediately preceding transmission period, thereby determining when to transmit a beacon signal in a given transmission period. The method may further include delaying transmission of the beacon signal for a given transmission period based on a determination that transmission of the other nodes is complete, thereby further determining when to transmit the beacon signal in the given transmission period.

Drawings

FIG. 1 is a diagram of an exemplary 10SPE network in accordance with examples of the present disclosure.

Fig. 2 is a diagram of an example transmission period according to an example of the present disclosure.

Fig. 3 is a diagram of timing of an example transmission period according to an example of the present disclosure.

Fig. 4-9 illustrate EMI generated by a 10SPE node under various conditions according to examples of the present disclosure.

Fig. 10 is an illustration of a timing diagram of time expansion or dithering of beacons according to an example of the present disclosure.

Fig. 11-12 illustrate noise reduction of EMI from time spreading or dithering of beacons according to examples of the present disclosure.

Fig. 13 illustrates an example method for time spreading or dithering of beacons according to an example of the present disclosure.

Fig. 14 illustrates an example method for time spreading or dithering of beacons, in which time spreading or dithering of beacons may be selectively applied, according to an example of the present disclosure.

Detailed Description

Examples of the present disclosure may include an apparatus. The apparatus may include a network interface configured to communicatively couple the apparatus to one or more other nodes in a network. The network interface may be any suitable network protocol, such as 10SPE. The apparatus may include a control circuit. The network interface and control circuitry may be implemented by analog circuitry, digital circuitry, instructions executed by a processor, or any suitable combination thereof. The network may include any suitable number and variety of nodes. The nodes may be physical or virtual electronic devices. The at least one node may be a network controller node, such as a PLCA controller node, configured to perform network allocation, assignment, or other management tasks on behalf of other nodes in the network. The tasks of the network controller node may be performed by a network management application. Each node may be implemented with a network driver or stack. The stack may be represented by the operation of the control circuitry. The control circuit may include or may be communicatively coupled to a PHY layer. Network traffic may be generated at a given node for communication with other nodes of the network. The control circuitry of a given node may be configured to repeatedly issue transmission cycles to other nodes over the network interface. A given transmission period may include at least one transmit time slot for each of the other nodes to transmit data. A transmit slot may be a time opportunity for a given node to transmit data. A given node may repeat a transmission cycle to the next node except that its own data is inserted at a given time. The control circuitry of a given node may be configured to initiate a transmission cycle by sending out beacon signals to other nodes. Determining when to transmit a beacon signal in a given transmission period may be performed by: it is determined that all other nodes have completed all associated transmit timeslots in the immediately preceding transmission cycle, thereby completing transmissions for other nodes. The beacon signal may also be delayed for a given transmission period.

In combination with any of the above embodiments, the control circuitry may be further configured to selectively delay transmission of the beacon signal for a given transmission period based on electromagnetic interference that may be generated from the device or other node. EMI may be measured or detected.

In combination with any of the above embodiments, the control circuit may be further configured to selectively delay transmission of the beacon signal for a given transmission period based on two or more additional immediately preceding transmission periods having a length shorter than a threshold. A particular threshold for a given system may be evaluated and an exemplary threshold may be less than two nodes using their respective transmit slots. Another exemplary threshold may be the number of minimum length transmission periods plus 10%.

In combination with any of the above embodiments, the control circuit may be further configured to selectively delay transmission of the beacon signal for a given transmission period based on two or more additional immediately preceding transmission periods having lengths within a threshold difference of each other. Such a threshold may be, for example, whether the two lengths are within 10%, 5% or 1% of each other.

In combination with any of the above embodiments, the control circuit may be further configured to set the transmission delay of the beacon signal for a given transmission period to be different from the non-zero transmission delay of the beacon signal for the immediately preceding transmission period.

In combination with any of the above embodiments, the control circuit may be further configured to set a variable transmission delay of the beacon signal for a given transmission period. The variable delay may vary between each transmission cycle.

In combination with any of the above embodiments, the control circuit may be further configured to set the transmission delay of the beacon signal for a given transmission period to a random value.

In combination with any of the above embodiments, the control circuit may be further configured to set a transmission delay of the beacon signal for a given transmission period according to a periodic function. The periodic function may include a sawtooth signal, a triangular signal, a sinusoidal signal, a ramp function, or any other suitable function or signal.

In combination with any of the above embodiments, the control circuit may be further configured to set a transmission delay of the beacon signal of a given transmission period according to a function, wherein the transmission delay of the beacon signal of the given transmission period is longer than the transmission delay of the beacon signal of an immediately preceding transmission period, wherein the transmission delay of the beacon signal of the immediately preceding transmission period is longer than the transmission delay of the beacon signal of another immediately preceding transmission period.

In combination with any of the above embodiments, the control circuit may be further configured to set a transmission delay of the beacon signal of a given transmission period according to a function, wherein the transmission delay of the beacon signal of the given transmission period is shorter than a transmission delay of the beacon signal of an immediately preceding transmission period, wherein the transmission delay of the beacon signal of the immediately preceding transmission period is shorter than a transmission delay of the beacon signal of another immediately preceding transmission period.

In combination with any of the above embodiments, the control circuit may be further configured to set a transmission delay of the beacon signal for the given transmission period by adding an additional transmission slot to the immediately preceding transmission period, wherein the additional transmission slot is configured to be unused by any node.

In combination with any of the above embodiments, the control circuit may be further configured to set a transmission delay of the beacon signal for a given transmission period by increasing quantization of a total number of nodes in the network.

Fig. 1 is a diagram of an exemplary 10SPE network 100 in accordance with an example of the present disclosure. As used in this disclosure, a 10SPE may refer to any 10SPE, 10Base-T1S, 10Base-T1L, or similar network. Network 100 may include any suitable number and variety of elements. These elements may include physical or virtual electronic devices. These may be referred to as nodes. For example, the network 100 may include nodes 102, 104A, 104B, 104C. The nodes may be configured to communicate with each other through the network medium 120. Network medium 120 may be implemented in any suitable manner, such as through a 10SPE network communication protocol.

Node 102 may be a network controller node, such as a PLCA controller node. Node 102 may act as a network controller node by performing network allocation, assignment, or other management tasks on behalf of other nodes in the network. Such tasks may be performed in node 102 by, for example, network management application 112. The nodes 102, 104A, 104B, 104C may each be implemented using a network driver or stack represented by the control circuit 106. The control circuit 106 may include or be communicatively coupled to a PHY layer 108. The nodes 102, 104A, 104B, 104C may each include one or more end user applications 110, a processor 114, and a memory 116.

End user application 110, network management application 112, and the network driver or stack represented by control circuitry 106 may include software, libraries, functions, scripts, applications, code, or other instructions for execution by processor 114. The instructions may be stored in respective memories 116. The instructions, when executed by the processor 114, may cause the user application 110, the network management application 112, and the control circuitry 106 to perform the functions of the present disclosure. The memory 116 may be implemented by one or more memory elements of any suitable implementation, whether long term or short term. The processor 114 may be implemented by one or more of any suitable processor, core, or microcontroller. Further, the control circuitry 106 may be implemented by any suitable instructions for execution by the processor 114 (as described above), analog circuitry, digital circuitry, or any suitable combination thereof.

The nodes 102, 104A, 104B, 104C may implement any suitable electronic devices, such as computers, laptops, servers, virtual machines, mobile devices, or automotive Electronic Control Units (ECUs). The nodes 102, 104A, 104B, 104C may each include different implementations of the end-user application 110. The end-user application 110 may need to communicate with other end-user applications in the end-user application 110 or other nodes in the nodes 102, 104A, 104B, 104C. Such communication may be performed, for example, using a 10SPE on network medium 120.

Although a number of nodes are shown in fig. 1, network 100 may include any suitable number and combination of 10 SPE-supported nodes.

Each node may be configured to perform traffic shaping. In one example, such shaping may be performed in hardware using digital logic. In another example, hooks may be implemented in the hardware of each node so that the firmware may also observe and shape the traffic. Traffic shaping may be performed to enforce bandwidth fairness or priority for time sensitive nodes.

Communication between nodes 102, 104A, 104B, 104C may be performed using transmission periods and frames shown in the following features. Each of the nodes 102, 104A, 104B, 104C may be configured to communicate with each other using frames consistent with the following examples.

Fig. 2 is a diagram 200 of an exemplary transmission period according to an example of the present disclosure. This transmission period may be used for the network 100 of fig. 1.

The first instance 202A of the transmission period may include a transmit time slot for each node of the network. If there are N nodes in the network, N transmit time slots may be included in a given transmission period. For example, the transmission period 202A may include transmission slots 210, 212, 214. Each such transmission slot may be assigned to a given node. The transmission time slots may be identified with an identifier (0 … N-1) that is unique to the transmission period. The identifier may identify the sender of the data packet. Each transmit slot may contain up to a certain amount of data 206. As discussed further below, in some examples, the assigned transmission slots may not have any data. The identifier may be included in the data 206. The identifier may identify the sender of the data. In various examples, the transmit time slots may be omitted for a given node under conditions discussed in further detail below. The transmit slots 210, 212, 214 may be separated by a period of silence 208. Each transmission period 202 may be initiated by a beacon 204. Beacon 204 may contain a suitable message to indicate that the transmission period is beginning. The beacon 204 and the transmit time slot 210 may be separated by a period of silence 208. The transmission period 202A may end and another transmission period 202B may begin. The participation of individual nodes in a given transmission period 202 may vary between transmission periods.

Upon receipt of the transmission period 202, a given node may parse it. The beacon 216 may be analyzed to determine the transmission period 202. The absence of silence 208 or data may be interpreted as determining a separate data portion of the next transmission period 202 to be received. The data 206 may be analyzed to determine whether it contains data to or from a given node. The given node may insert its own data 206 into the transmission cycle.

The transmission period may reflect shaping traffic in the network with PLCA. PLCA may be specified in IEEE p802.3cg. PLCA may provide access fairness to nodes in a network. Access fairness may include each node's ability to access the network in a given transmission period 202. However, PLCA does not provide bandwidth fairness or priority among nodes. Bandwidth fairness may not be provided because a given node may insert more data into their packets than other nodes even if access fairness is provided. Furthermore, access fairness cannot provide any priority among nodes. Examples of the present disclosure may provide bandwidth fairness and priority among nodes. The PLCA and its enhancements may be implemented in digital logic or instructions for execution in the network stack. The PLCA and its enhancements may include hooks for firmware to observe and shape the traffic.

For most implementations of conflict-based networks, the maximum bandwidth utilization may be only 60%. Furthermore, without deterministic behavior, it may not be used for safety critical applications. In contrast, for PLCA, a network controller node (such as node 102) may organize network access at the physical layer. This can prevent collisions, provide deterministic behavior, and fully use bandwidth.

In fig. 2, each PHY of a respective node may be assigned a static ID (0..n-1). The network controller node may have an ID of "0". The network controller node may send a beacon 204 to begin a new transmission period. Upon reception, each of the other nodes may have an opportunity to transmit data in a respective transmit slot 210, 212, 214 via a respective PHY hardware or software. In one example, a node may present or create an opportunity to transmit data in respective transmit slots 210, 212, 214. If silence 208 exceeds a given threshold, other nodes may be configured to recognize that the given node has skipped its opportunity to transmit data. Then, the next transmission slot may begin.

Fig. 3 is a diagram 300 of timing of an exemplary transmission period according to an example of the present disclosure. The minimum time and maximum time to complete a transfer cycle or bus cycle may be calculated.

The minimum time required to complete a complete transmission cycle can be given as follows:

Minimum bus cycle time = tbaco+ (n+1) tstart

Where tstargetis the time required to transmit a beacon 204, tstargetis the time required to silence 208 between a pair of transmit slots, and N is the number of nodes or transmit slots. Such a minimum time would occur if all nodes had created their opportunity to use their respective transmit slots. the value of tstart is multiplied by (n+1) to account for the period of silence 208 after each of the N nodes and another period of silence 208 between the beacon 204 and the first transmit slot.

The maximum time required to complete a complete transmission cycle can be given as follows:

maximum bus cycle time = tbaco+ (n+1) tstard +n tMTU

Where tstargetis is the time required to transmit a beacon 204, tstargetis is the time required to silence between a pair of transmit slots, tMTU is the time required to transmit the longest allowed data length (MTU-maximum transmission unit), and N is the number of nodes or transmit slots. Such maximum time will occur if all nodes transmit their data using the maximum time between transmission slots (thus utilizing the full amount of silence), all nodes transmit data using their transmission slots, and all nodes transmit the maximum amount of data in their respective transmission slots. In one example, the MTU may be 64 bytes in length. Silence 208 timeout periods may be included in this calculation because a given node may wait for the duration of the silence timeout period before transmitting.

In a given transmission cycle, data, whether transmitted in the form of beacons 204 or data 206, may cause the node transmitting the data to transmit EMI. The amount of EMI may vary depending on the content of the data transmitted, the length of the data transmitted, the frequency at which the transmission cycle is repeated, the periodicity of the transmission cycle, or other suitable factors. Examples of the present disclosure may reduce EMI transmissions by applying a delay at the end of a given transmission period.

The nodes 102, 104 may include output drivers (not shown) that may, for example, drive a communication bus on the network medium 120 to the other nodes 102, 104. The nodes 102, 104 may be in a high impedance idle or receive state when they are not capable of generating an output. Transition to and from these states and the driver's own common mode voltage input and output levels can create inherent common mode noise.

Fig. 4-9 illustrate EMI generated by a 10SPE node under various conditions according to examples of the present disclosure. In particular, the common mode noise of a given node 102, 104 under different conditions is shown in fig. 4 to 9. While this common mode noise can be reduced by careful driver design, it may still occur. In addition, changes in driver design require changes in die size, typically increases in die size.

A10 SPE system such as system 100 may rely on a periodically repeated beacon bit pattern for its operation. The repetition period may be constant, such as in the case of a bus idle or low bus utilization. Thus, the naturally occurring common mode noise of the driver causes energy accumulation in the corresponding frequency, which eventually becomes EMI.

FIG. 4 illustrates the EMI generated when the bus of the network medium 120 between the 10SPE nodes 102, 104 is fully idle. The limits of EMI noise are shown. The limit is represented by a line whose amplitude varies according to the frequency variation. The limit may be defined in any suitable manner, such as according to a communication protocol or experimental data. The limit may define any suitable acceptable limit above which EMI noise is considered to be potentially problematic for other equipment. The data diagram shown in fig. 4 is the signal observed at a given node. When the noise on the network medium 120 is sufficiently high and the subsequent signal exceeds this limit, the noise generated may be considered too high. In the case of fig. 4, the noise does not come close to exceeding the limit.

Fig. 5 shows the EMI generated when 10SPE nodes 102, 104 issue a transmission cycle, but no node uses its transmit time slot, leaving only a beacon signal at the beginning of each transmission cycle. Further, in the example of fig. 5, there may be one node instance, such as node 102.

As shown in fig. 5, the EMI disturbance approaches or even touches the limit line, reflecting unacceptably large noise. The noise may be in-band. The in-band frequencies may include a range of frequencies that are related to or required for proper data recovery, in contrast to out-of-band frequencies where signals are not related to or required for data recovery. Simply filtering out the in-band frequencies of noise may have the adverse side effect of degrading the signal required to indicate the data. For example, if the signal is filtered for a frequency range of in-band noise, the actual data carried by the signal may be filtered out. Thus, filtering the noise type shown in fig. 5 may be an inadequate solution. This may be in contrast to filtering out-of-band noise, which may be done safely and without degrading the data transmitted in the signal.

Fig. 6 shows the EMI generated when 10SPE nodes 102, 104 issue a transmission cycle, but no node uses its transmit time slot, leaving only a beacon signal at the beginning of each transmission cycle. Further, in the example of fig. 6, there may be eight instances of nodes, such as node 102 and seven nodes 104.

As shown in fig. 6, the EMI interference may not be as severe as the EMI interference shown in fig. 5. Thus, if the period of the transmission period is longer, or if more nodes are used, EMI interference can be reduced.

Fig. 7 illustrates EMI generated when 10SPE nodes 102, 104 in network medium 120 issue a transmission cycle, where the nodes use the transmit time slots to transmit messages of maximum length of data.

As shown in fig. 7, EMI interference may be at an acceptably low level below the limit line. Thus, if the nodes 102, 104 transmit longer messages, EMI interference may be reduced.

Fig. 8 shows EMI generated when 10SPE nodes 102, 104 in network medium 120 issue messages with short non-empty data payloads, and there are two instances of nodes 102, 104, such as an instance of each of nodes 102 and 104. The short data payload may be, for example, 20% of the maximum allowed length.

As shown in fig. 8, EMI interference approaches or even touches the limit line, reflecting unacceptably large noise. The noise may be in-band. This may occur even if the message is longer than the message in fig. 5.

Fig. 9 shows EMI generated when 10SPE nodes 102, 104 in network medium 120 send out messages with short non-empty data payloads, and there are eight instances of nodes, such as node 102 and seven nodes 104.

As shown in fig. 9, EMI interference may be within acceptable levels. Thus, EMI interference may not be as severe as shown in fig. 8, where more nodes of the network transmit longer messages in fig. 9.

Accordingly, the inventors of examples of the present disclosure found that in bus systems (such as 10 SPEs) that utilize undriven idle states (such as empty transmission opportunities), a pattern (such as a beacon signal) that repeats at a constant rate can result in increased EMI levels. As described above, EMI may be caused by inherent common mode changes originating from transitions from idle to driving states and back to idle states in the nodes 102, 104. In particular, for PLCA implementations, with low bus utilization, if the repeated beacon pattern occurs at a fixed rate, it may be the largest EMI contributor.

In one example, the control circuitry 106A of the network controller node 102 may be configured to perform time spreading or dithering of the beacon signal. This may be performed on any suitable basis, such as in response to detected EMI, in response to potential EMI, or may be prophylactic or active in nature. In one example, time expansion may be achieved by adding a delay at the end of each period. This may include adding such delays before the start of a subsequent cycle. In another example, the length of the delay may be dynamically varied.

Thus, the time occurrence or periodicity of the beacon may be modulated. This in turn has the effect of expanding the frequency footprint of the EMI noise generated, resulting in lower peaks of EMI. In order not to impair the bus/network bandwidth, the variable delay may be added only to periods where no transmission is occurring or to transmissions that would result in repetition of the previous transmission period length. The delay may be generated by any suitable function, such as by a random, pseudo-random, triangular, saw tooth, or ramp function. For example, the delay may be generated by a trigonometric function, where the delay is increased or decreased by one bit per period. The solution can be implemented in digital implementations without the need to optimize analog changes that are inherently easy to change. The overhead of implementation and verification is very small, but the expected impact on emissions has an emission level improvement on the order of 10dB to 15dB in the critical area.

Fig. 10 illustrates a timing diagram of time expansion or dithering of beacons according to an example of the present disclosure. The timing diagram of fig. 10 may reflect, for example, the operation of the cycle generated by the network controller node 102.

As described above, the network controller node 102 may be configured to initiate a transmission cycle by sending out beacon signals to other nodes. The network controller node 102 may be configured to determine when to transmit a beacon signal in a given transmission period.

The network controller node 102 may be configured to determine, for a given transmission period X, whether all other nodes 104 have completed all associated transmit timeslots in the immediately preceding transmission period X-1, thereby completing transmissions for the other nodes. The network controller node 102 may be configured to delay transmission of the beacon signal for transmission period X based on a determination that transmission of other nodes in transmission period X-1 is complete. This may be represented by a dynamically variable delay added to the end of transmission period X-1, thereby delaying transmission period X by delaying the beacon used to start transmission period X.

Similarly, the network controller node 102 may be configured to determine, for a given transmission period x+1, whether all other nodes 104 have completed all associated transmit timeslots in the immediately preceding transmission period X, thereby completing transmissions for the other nodes. The network controller node 102 may be configured to delay transmission of the beacon signal for transmission period x+1 based on a determination that transmission of other nodes in transmission period N is complete. This may be represented by a dynamically variable delay added to the end of transmission period X, thereby delaying transmission period x+1 by delaying the beacon used to start transmission period x+1. The particular value of the dynamically variable delay used in the transmission period may be different from the particular value of the dynamically variable delay used in the previous or subsequent transmission period.

Such delays may be added to the end of any suitable number of cycles, such as X-1, X, and X+1 as shown in FIG. 10. Delays added to the ends of periods X-1, X, and X+1 may each have different values or lengths.

The network controller node 102 may be configured to selectively delay transmission of the beacon signal for a given transmission period, wherein the network controller node 102 may be configured to turn on or off insertion of the delay. The network controller node 102 may be configured to delay transmission of the beacon signal for a given transmission period on any suitable basis. For example, the network controller node 102 may be configured to selectively delay transmission of the beacon signal for a given transmission period based on the potential for EMI generation from either of the nodes 102, 104. This can be predicted based on, for example, a given number of repetition periods of a given similar length or a given number of repetition periods of the same length below a given length. Further, settings for selectively delaying transmission of the beacon signal, such as EMI levels or the number of repeated cycles, may be based on user or system settings and stored in, for example, a register (not shown).

In one example, the network controller node 102 may be configured to selectively delay transmission of the beacon signal for a given transmission period (such as x+1) based on two or more additional immediately preceding transmission periods (X, X-1) having a length shorter than a threshold. A particular threshold for a given system may be evaluated and an exemplary threshold may be less than two nodes using their respective transmit slots. Another exemplary threshold may be the number of minimum length transmission periods plus 10%. In another example, the network controller node 102 may be configured to selectively delay transmission of the beacon signal for a given transmission period (such as x+1) based on two or more additional immediately preceding transmission periods (X-2, X-1) having lengths that are approximately equal and within a threshold difference of each other. Such a threshold may be, for example, whether the two lengths are within 10%, 5% or 1% of each other. In yet another example, the network controller node 102 may be configured to selectively delay transmission of the beacon signal for a given transmission period (such as x+1) based on two or more additional immediately preceding transmission periods (X, X-1) having lengths that are shorter than a threshold and that are approximately equal and within a threshold difference of each other. Such a threshold may be, for example, whether the two lengths are within 10%, 5% or 1% of each other.

The network controller node 102 may be configured to set the transmission delay of the beacon signal for a given transmission period (such as x+1) to be different from the non-zero transmission delay of the beacon signal for the immediately preceding transmission period (such as X). That is, the delay of period x+1 may be a non-zero delay that is different from the delay of period X, which is also a non-zero delay. The amount of delay may be any suitable value. Such suitable values may include values that vary from transmission period to transmission period. In one example, the network controller node 102 may be configured to set the transmission delay of the beacon signal for a given transmission period to a random value. In another example, the network controller node 102 may be configured to set the transmission delay of the beacon signal for a given transmission period according to a periodic function.

For example, the network controller node 102 may be configured to set the transmission delay of the beacon signal for a given transmission period (x+1) according to a trigonometric function, wherein the delay between any two given transmission periods varies only by a small amount. The transmission delay of the beacon signal of a given transmission period (x+1) is longer than the transmission delay of the beacon signal of an immediately preceding transmission period (X), wherein the transmission delay of the beacon signal of the immediately preceding transmission period (X) is longer than the transmission delay of the beacon signal of another immediately preceding transmission period (X-1). This process may continue until the delay peaks at, for example, time Y. Subsequently, the network controller node 102 may be configured to set the transmission delay of the beacon signal of another given transmission period (y+1) further according to a trigonometric function, wherein the transmission delay of the beacon signal of the given transmission period (y+1) is shorter than the transmission delay of the beacon signal of the immediately preceding transmission period (Y). The transmission delay of the beacon signal for the next transmission period (y+2) will be shorter than the transmission delay of the beacon signal for the given transmission period (y+1). This may continue until the delay reaches a minimum, and thereafter the delay may be incrementally increased. Similarly, a sawtooth function, a ramp function, a reverse ramp function, a sinusoidal function, a random function, or a pseudo-random function may be used.

Although the length of the delay provided by the network controller node 102 may be variable, the maximum length of the delay may be shorter than the length of the unused transmit time slots of one of the other nodes.

In one example, the network controller node 102 may be configured to set the transmission delay of the beacon signal for a given transmission period (such as x+1) by adding an additional transmit time slot to the immediately preceding transmission period (X). For example, additional transmit time slots may be added to each transmission period until a maximum value is reached, where the transmit time slots may be reduced to an initial value.

In one example, the network controller node 102 may be configured to set the transmission delay of the beacon signal for a given transmission period by increasing the quantized representation of the number of nodes 104 in the system 100. For example, system 100 may include 10 instances of node 104. Each node 104 may know from a setting such as MaxID that there are 10 instances of the node 104. Each node 104 may use this information to know when it will be its transmission slot. MaxID may be a quantification of the total number of nodes 104 and network controller nodes 102. The network controller node 102 may be configured to delay transmission of the beacon signal for a given transmission period X by increasing MaxID for that transmission period beyond a value that is actually necessary to represent the number of nodes in the network 100. Each node 104 may then expect that the transmission period will terminate after a number of nodes have a transmission opportunity or transmit time slot.

Fig. 11-12 illustrate noise reduction of EMI from time spreading or dithering of beacons according to examples of the present disclosure. Fig. 11 illustrates EMI generated by different configurations of the network controller node 102 to perform time spreading or dithering of beacons. Fig. 12 may be a more detailed view of fig. 11.

As shown in fig. 11-12, in a first curve 1102, the highest peak of EMI may result from repeated messages sent out in the network medium 120 without time spreading or jitter of the beacons. In the second curve 1104 and the third curve 1106, time spreading or dithering of beacons may be applied. For example, a delay may have been added to the end of each transmission period. By using trigonometric functions, the delay can vary from cycle to cycle. In the second curve 1104 and the third curve 1106, a trigonometric function with a period of 20 cycles or steps may be used to generate the delay. In the second curve 1104, the trigonometric function may include a delay step size of 40ns per step. Thus, the delay added to the period will be progressively selected from {0ns, 40ns, 80ns, 120ns, … 760ns, 800ns, 760ns, 720ns … ns, 40ns, 0ns, 40ns, 80ns … }. In the third curve 1106, the trigonometric function may include a delay step size of 80ns per step. Thus, the delay added to the period will be progressively selected from {0ns, 80ns, 160ns, 240ns, … 1520ns, 1600ns, 1520ns, … 80ns, 0ns, 80ns … }.

As shown in fig. 11-12, both the second curve 1104 and the third curve 1106 demonstrate that EMI is reduced by adding a variable delay to each transmission cycle, as compared to the first curve 1102. However, the difference between the second curve 1104 and the third curve 1106 may indicate that as the step size of the exemplary delay increases between 40ns and 80ns, the return for reducing EMI also decreases. In view of effectiveness and other design considerations, particular functions for creating delays (such as triangle, ramp, saw tooth, or random functions) and parameters of such particular functions (such as step size or step size count) may be evaluated in particular implementations. For example, while the 80ns step shown in the third curve 1106 further reduces EMI compared to the 40ns step shown in the second curve 1104, this is at the cost of further delay. Each variable delay increases the delay of the transmission period, thereby reducing the bandwidth of the network medium 120.

Furthermore, the inventors of the examples of the present disclosure found that when the difference between the subsequent delays is substantial, a decrease in return for reducing EMI, or even an increase in EMI, may occur if the difference between the two subsequent delays is sufficiently large. For example, if a ramp function is used to generate the delay, at the peak of the ramp function, the generated delay may be 800ns. The next delay value returned by the ramp function may be 0ns. The difference in the two generated delays (800 ns) may be much larger than other functions, such as trigonometric functions. The use of trigonometric functions may provide the benefit of synchronization.

Examples of the present disclosure may be implemented by making digital logic or software changes to existing implementations of the nodes 102, 104. Such changes may work with existing analog front ends or other components. Further, examples of the present disclosure may operate within a system that uses existing 10SPE specifications. Further, implementations of examples of the present disclosure may be performed in the network controller node 102 without requiring changes to the node 104.

Fig. 13 is an illustration of an example method 1300 for time spreading or dithering of beacons in accordance with an example of the present disclosure. The method 1300 may be implemented by, for example, the system 100 and in particular by the network controller node 102. Further, the method 1300 may be performed by the control circuit 106A of the network controller node 102. Method 1300 may include more or fewer blocks than shown in fig. 13. The blocks of method 1300 may be performed in any suitable order, and blocks may optionally be repeated, recursively performed, or omitted.

At block 1305, operations of the method may be initialized. System or operating preferences, such as specifications for noise correction, may be read. These may include, for example, specifications of the type of delay to be applied. These preferences may be specified by a user, manufacturer, or system software and may be provided in memory or in hardware (such as through fuses).

At block 1310, a determination may be made as to what type of time expansion or dithering of the beacon is to be performed. Specifically, the type of delay to be used may be determined. If a periodic function is to be performed, the method 1300 may proceed to block 1315. If random delay is to be performed, the method 1300 may proceed to block 1325. If a change in the number of expected nodes in the system represented by the MaxID value is to be performed, the method 1300 may proceed to block 1335.

At block 1315, one or more delays may be generated using a periodic function, such as a triangle, ramp, saw tooth, sine, or other function. The amplitude, step size, number of steps, number of time periods, or other parameters may be determined according to system or user settings. The function may be used to generate delays of different sizes and to add each variable delay to the end of the transmission period. This may be performed for a given number of cycles. The method 1300 may proceed to block 1320. At block 1320, it may be determined whether time expansion or jitter will continue. If so, the method 1300 may repeat at block 1315, for example. Otherwise, the method 1300 may proceed to block 1345.

At block 1325, one or more delays may be generated using the random number. The length of the delay may be randomly selected between zero and the maximum delay length. The maximum delay length may be set to, for example, the time required for the minimum size of the transmission time slot for the node 104. The given number of cycles of execution delay may be determined based on system or user settings. The size of the delay may vary and may be added to the end of the transmission period. This may be performed for a given number of cycles. At block 1330, it may be determined whether time expansion or dithering will continue. If so, the method 1300 may repeat at block 1325, for example. Otherwise, the method 1300 may proceed to block 1345.

At block 1335, an indication of the number of system nodes may be changed. The indication may be given as MaxID. For a given number of cycles, the MaxID value may be changed. The result may be that the node of the system waits for an additional amount of time based on the increase in MaxID values. At block 1340, it may be determined whether time expansion or jitter will continue. If so, method 1300 may repeat at block 1335, for example. Otherwise, the method 1300 may proceed to block 1345.

At block 1345, the method 1300 may terminate.

Fig. 14 is an illustration of an example method 1400 for time spreading or dithering of beacons in which time spreading or dithering of beacons may be selectively applied, according to an example of the present disclosure. The method 1400 may be implemented by, for example, the system 100 and in particular by the network controller node 102. Further, the method 1400 may be performed by the control circuit 106A of the network controller node 102. Method 1400 may include more or fewer blocks than shown in fig. 14. The blocks of method 1300 may be performed in any suitable order, and blocks may optionally be repeated, recursively performed, or omitted.

At block 1405, the operations of the method may be initialized. The system or operational preferences, such as a definition of the level of noise (such as EMI) may be read. Furthermore, available corrections to noise, such as the type of delay to be applied, may be read. These preferences may be specified by a user, manufacturer, or system software. These preferences may be provided in memory (such as in registers) or in hardware (such as through fuses).

At block 1410, successive transmission periods in the network may be observed. The length of the transmission periods can be observed, as well as the similarity of the transmission periods to each other.

At block 1415, it may be determined whether to use time spreading or dithering of the beacon. This may be determined based on whether a threshold level of EMI has been detected. Further, this may be determined based on whether a threshold level of EMI has been predicted. In various examples, this may include determining that a threshold number of consecutive cycles have been observed, where each cycle is below a threshold size or within a threshold amount of similarity. In other examples, such as shown in fig. 13, time spreading or dithering of beacons may be enabled to be used regardless of whether EMI has been detected or predicted. If EMI is observed or predicted, time spreading or dithering of the beacons may be used. If time spreading or dithering of beacons is to be used, the method 1400 may proceed to block 1420. Otherwise, the method 1400 may proceed to block 1445.

At block 1420, a determination may be made as to what type of time spreading or dithering of beacons is to be performed. In particular, the type of delay used to implement the time expansion or dithering of the beacon may be determined. If a periodic function is to be performed, the method 1400 may proceed to block 1425. If random delay is to be performed, the method 1400 may proceed to block 1430. If a change in the number of expected nodes in the system represented by the MaxID value is to be performed, the method 1400 may proceed to block 1435.

At block 1425, one or more delays may be generated using periodic functions, such as triangles, ramps, serrations, sinusoids, or other functions. The magnitude, frame size, number of frames, number of time periods, or other parameters may be determined according to system or user settings. The function may be used to generate delays of different sizes and to add each variable delay to the end of the transmission period. This may be performed for a given number of cycles. The method 1400 may proceed to block 1440.

At block 1430, one or more delays may be generated using a random function. The length of the delay may be randomly selected between zero and the maximum delay length. The maximum delay length may be set to, for example, the time required for the minimum size of the transmission time slot for the node 104. The given number of cycles of execution delay may be determined based on system or user settings. The size of the delay may vary and may be added to the end of the transmission period. This may be performed for a given number of cycles. The method 1400 may proceed to block 1440.

At block 1435, an indication of the number of system nodes may be changed. The indication may be given as MaxID. For a given number of cycles, the MaxID value may be changed. The result may be that the node of the system waits for an additional amount of time based on the increase in MaxID values. The method 1300 may proceed to block 1440.

At block 1440, it may be determined whether time expansion or dithering of the beacon will continue. The determination may be made in the same manner as determined in block 1410. If so, the method 1400 may return to block 1420, or to a previously selected block of blocks 1425, 1430, 1435. If not, the method 1400 may proceed to block 1450.

At block 1445, a normal period and beacon schedule may be maintained. The method 1400 may proceed to block 1450.

At block 1450, a determination may be made as to whether the method 1400 is to continue. If so, the method 1400 may repeat at block 1410, for example. Otherwise, at block 1455, the method 1400 may terminate.

Although examples have been described above, the present disclosure may have other modifications and examples without departing from the spirit and scope of these examples.

Claims

1. An apparatus, the apparatus comprising:

a network interface configured to communicatively couple the apparatus to one or more other nodes in a network; and

A control circuit configured to:

Repeatedly issuing a transmission period to the other nodes through the network interface, wherein a given transmission period includes at least one transmission time slot for each of the other nodes to transmit data;

initiating a transmission period by sending out a beacon signal to the other node; and

Determining when to transmit a beacon signal in a given transmission period by:

Determining that all of the other nodes have completed all associated transmit timeslots in an immediately preceding transmission period, thereby completing transmission of the other nodes; and

Based on the determination of the completion of the transmission of the other node, the transmission of the beacon signal for the given transmission period is selectively delayed based on two or more further immediately preceding transmission periods having a length shorter than a threshold or a length within a threshold difference of each other.

2. The apparatus of claim 1, wherein the control circuitry is further configured to selectively delay transmission of the beacon signal for the given transmission period based on electromagnetic interference that may be generated according to the apparatus or the other node.

3. The apparatus of any of claims 1-2, wherein the control circuitry is further configured to set a transmission delay of the beacon signal for the given transmission period to be different from a non-zero transmission delay of a beacon signal for the immediately preceding transmission period.

4. The apparatus of any of claims 1-2, wherein the control circuitry is further configured to set a variable transmission delay of the beacon signal for the given transmission period.

5. The apparatus of any of claims 1-2, wherein the control circuitry is further configured to set a transmission delay of the beacon signal for the given transmission period to a random value.

6. The apparatus of any of claims 1-2, wherein the control circuit is further configured to set a transmission delay of the beacon signal for the given transmission period according to a periodic function.

7. The apparatus of any of claims 1-2, wherein the control circuitry is further configured to set a transmission delay of the beacon signal for the given transmission period according to a function, wherein the transmission delay of the beacon signal for the given transmission period is longer than a transmission delay of a beacon signal for the immediately preceding transmission period, wherein the transmission delay of the beacon signal for the immediately preceding transmission period is longer than a transmission delay of a beacon signal for another immediately preceding transmission period.

8. The apparatus of any of claims 1-2, wherein the control circuit is further configured to set a transmission delay of the beacon signal for the given transmission period according to a function, wherein the transmission delay of the beacon signal for the given transmission period is shorter than a transmission delay of a beacon signal for the immediately preceding transmission period, wherein the transmission delay of the beacon signal for the immediately preceding transmission period is shorter than a transmission delay of a beacon signal for another immediately preceding transmission period.

9. The apparatus of any of claims 1-2, wherein the control circuitry is further configured to set a transmission delay of the beacon signal for the given transmission period by adding an additional transmission slot to the immediately preceding transmission period, wherein the additional transmission slot is configured to be unused by any of the nodes.

10. The apparatus of any of claims 1-2, wherein the control circuitry is further configured to set a transmission delay of the beacon signal for the given transmission period by increasing quantization of a total number of nodes in the network.

11. A method for time expansion of beacons, the method comprising: at a node in a network, operations are performed by any one of the control circuits of any one of the devices according to any one of claims 1 to 10.

12. A non-transitory machine readable medium comprising instructions that, when loaded and executed by a processor, cause the processor to implement operations performed by control circuitry of any one of the apparatus of any one of claims 1 to 10.